From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71D51C43142 for ; Fri, 22 Jun 2018 09:56:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 34A7223FD4 for ; Fri, 22 Jun 2018 09:56:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 34A7223FD4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=alien8.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933664AbeFVJ4f (ORCPT ); Fri, 22 Jun 2018 05:56:35 -0400 Received: from mail.skyhub.de ([5.9.137.197]:41270 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754626AbeFVJyc (ORCPT ); Fri, 22 Jun 2018 05:54:32 -0400 X-Virus-Scanned: Nedap ESD1 at mail.skyhub.de Received: from mail.skyhub.de ([127.0.0.1]) by localhost (blast.alien8.de [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id r1a1G7of6xPD; Fri, 22 Jun 2018 11:54:31 +0200 (CEST) Received: from zn.tnic (p200300EC2BCF3400329C23FFFEA6A903.dip0.t-ipconnect.de [IPv6:2003:ec:2bcf:3400:329c:23ff:fea6:a903]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 5B8911EC0236; Fri, 22 Jun 2018 11:54:31 +0200 (CEST) From: Borislav Petkov To: X86 ML Cc: LKML Subject: [PATCH 1/7] x86/mce: Always use 64-bit timestamps Date: Fri, 22 Jun 2018 11:54:22 +0200 Message-Id: <20180622095428.626-2-bp@alien8.de> X-Mailer: git-send-email 2.17.0.582.gccdcbd54c In-Reply-To: <20180622095428.626-1-bp@alien8.de> References: <20180622095428.626-1-bp@alien8.de> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Arnd Bergmann The machine check timestamp uses get_seconds(), which returns an 'unsigned long' number that might overflow on 32-bit architectures (in the distant future) and is therefore deprecated. The normal replacement would be ktime_get_real_seconds(), but that needs to use a sequence lock that might cause a deadlock if the MCE happens at just the wrong moment. The __ktime_get_real_seconds() skips that lock and is safer here, but has a miniscule risk of returning the wrong time when we read it on a 32-bit architecture at the same time as updating the epoch, i.e. from before y2106 overflow time to after, or vice versa. This seems to be an acceptable risk in this particular case, and is the same thing we do in kdb. Signed-off-by: Arnd Bergmann Acked-by: Thomas Gleixner Cc: Tony Luck Cc: linux-edac Cc: x86-ml Cc: y2038@lists.linaro.org Link: http://lkml.kernel.org/r/20180618100759.1921750-1-arnd@arndb.de Signed-off-by: Borislav Petkov --- arch/x86/kernel/cpu/mcheck/mce.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index e4cf6ff1c2e1..b887415652ed 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -123,8 +123,8 @@ void mce_setup(struct mce *m) { memset(m, 0, sizeof(struct mce)); m->cpu = m->extcpu = smp_processor_id(); - /* We hope get_seconds stays lockless */ - m->time = get_seconds(); + /* need the internal __ version to avoid deadlocks */ + m->time = __ktime_get_real_seconds(); m->cpuvendor = boot_cpu_data.x86_vendor; m->cpuid = cpuid_eax(1); m->socketid = cpu_data(m->extcpu).phys_proc_id; -- 2.17.0.582.gccdcbd54c